1. Technical Field
This invention relates to a roof bolt bearing plate and method for use in underground mining operations. In one aspect, this invention relates to a roof bolt bearing plate and method for supporting the roof in an underground coal mine.
2. Background
Mining operations today use roof bolt bearing plates to support the roofs in underground mines.
Support integrity for the mine roof provides a safe work place and maintains the important safety required for working in an underground mine. Failure to control the stability of the roof of the mine leads to the majority of serious or fatal accidents occurring in underground mines in the United States today. Accidents involving major cave-ins of mine roofs have become less prevalent, but a fatal accident can occur from the falling of large rock from the roof of a mine. Accordingly, mine roof control systems must provide safety integrity for personnel working in the mines. The Mine Safety and Health Administration (MSHA) of the United States government enforces mine safety standards, including roof support standards, and inspects mine roof control plans and practices in the mining industry.
Enhanced safety and roof support have reduced serious accidents involving major roof cave-ins substantially since the 1970's. Compliance with MSHA standards now requires underground mines to have a roof control plan in place, and such plan includes “primary roof support.” Primary roof support includes abatement provisions designed to prevent a roof cave-in by sealing the lowest layers of a mine roof to upper strata of rock.
Methods for attaching lower level rock strata to upper layers use a roof bolt and epoxy resin to seal layers of rock strata. Roof bolts vary in length and size but are typically one-half inch or more in diameter and 30 inches to 12 feet long or longer in overall length. A motorized roof bolter places a roof bolt in a roof ceiling. Positioned in the front, unprotected face of the mine, a drilling mechanism drills several feet up through the mine roof. After a hole is placed in the roof, an epoxy resin in a pliable plastic tube is inserted in the hole. Next, a roof bolt is placed in the hole, and the placing of the roof bolt tears the packaging for the epoxy resin and mixes the resin to the bolt itself and the surrounding rock layers. The epoxy resin typically “sets up” or hardens within a matter of seconds, and the bolt and rock layers are sealed to each other.
In most underground mining situations, a roof bolt is placed approximately every four feet in the mine. Accordingly, placement of the roof support is a major undertaking and a major source of expense for the mine operator. Despite the cost, roof bolt and epoxy combinations are the conventional means for providing primary roof support and meet the requirements promulgated by MSHA and various state enforcement authorities.